Filter拦截Ajax向Servlet的请求的问题

迷南。 2022-05-21 09:25 167阅读 0赞

过滤器拦截Ajax请求是，chain.doFiltetr报错误。

经过半天的琢磨，原来是jar包的问题。使用AJAX传送JSON数据，需要导入7个jar包，并且要注意版本的搭配。我就是随便下载版本导致的问题。

PS：AJAX中，当服务器状态就绪后，需要执行的代码要放在if语句块中。如果在JS中定义了一个全局变量var str。在onreadystatechange函数中不能为此变量赋值。str在函数外依然为空。

还有，responseText中文乱码的问题。在Servlet中，需要设置response.setCharacterEncoding(xxx)。总之，Servlet编码、传送的数据的编码和JSP页面的编码要保持一致。

下面贴上JSP页面和Servlet页面的代码。这不是一个完整的项目，这两个代码是正确的，其余的JSP和javabean这里就不贴了。

bookQueryAll.jsp:

<%@ page contentType="text/html; charset=utf-8" language="java" errorPage="" %>
    <%@ page import="java.util.List,domin.*" %>
    <!DOCTYPE html>
    <html>
    <head>
    	<meta charset="utf-8">
    	<title>图书查询</title>
    	<style>
    		h2{
    			text-align:center;
    		}
    		#query{
    			text-align:center;
    		}
    		table{
    			border-collapse:collapse;
    			width:600px;
    			margin:0 auto;
    		}
    		td {
    			border:1px solid black;
    		}
    		#thead {
    			text-align:center;
    		}
    	</style>
    	<script>
    		var xmlhttp;
    		if(window.XMLHttpRequest){
    			xmlhttp = new XMLHttpRequest();
    		}else{
    			xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    		}
    		
    		xmlhttp.open("post","ajaxServlet","true");
    		xmlhttp.send();
    		xmlhttp.onreadystatechange=function(){
    			if(xmlhttp.readyState == 4 && xmlhttp.status == 200){
    				console.log("json获取成功");
    				json = JSON.parse(xmlhttp.responseText);
    				for(var i in json){
    					var book = json[i];
    					var bookId = book.bookId;
    					var bookName = book.bookName;
    					var bookCategory = book.bookCategory;
    					var bookPrice = book.bookPrice;
    					var bookDescription = book.bookDescription;
    					var tr = document.createElement("tr");
    					var td1 = document.createElement("td");
    					var td2 = document.createElement("td");
    					var td3 = document.createElement("td");
    					var td4 = document.createElement("td");
    					var td5 = document.createElement("td");
    					console.log(bookName);
    					tr.appendChild(td1);
    					tr.appendChild(td2);
    					tr.appendChild(td3);
    					tr.appendChild(td4);
    					tr.appendChild(td5);
    					td1.innerHTML = bookId;
    					td2.innerHTML = bookName;
    					td3.innerHTML = bookCategory;
    					td4.innerHTML = bookPrice;
    					td5.innerHTML = bookDescription;
    					var table = document.getElementById("ajax");
    					table.appendChild(tr);
    				}
    			}else{
    				console.log("json获取失败");
    			}
    		}
    		
    	</script>
    </head>
    <body>
    	<h2>图书查询</h2>
    	<div id="query">图书ID：<input type="text" name="bookId"/>图书名：<input type="text" name="bookName"/>分类<input type="text" name="bookCategory"/>
    	<input type="submit" /></div>
    	<hr>
    	<table id="ajax">
    		<tr id="thead">
    			<td>图书ID</td>
    			<td>书名</td>
    			<td>分类</td>
    			<td>价格</td>
    			<td>描述</td>
    		</tr>
    		
    	<table>
    </body>
    </html>

AjaxServlet.java:

package servlet;
    import domin.*;
    import service.*;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import net.sf.json.JSONArray;
    import java.util.List;
    
    @WebServlet(name="ajaxServlet",urlPatterns={"/ajaxServlet"})
    public class AjaxServlet extends HttpServlet{
    	@Override
    	public void init(ServletConfig config) throws ServletException{
    		super.init(config);
    	}
    	@Override
    	public void service(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{
    		LibServicelmpl libServicelmpl = new LibServicelmpl();
    		List<Book> books = libServicelmpl.getBooks();
    		JSONArray jsonArray = JSONArray.fromObject(books);
    		System.out.println("Ajax service执行");
    		response.setCharacterEncoding("utf-8");
    		response.getWriter().write(jsonArray.toString());
    	}
    }